The present invention relates to a bicycle trailer, and it is intended particularly, but not exclusively, for touring and cross-country bicycles commonly known as xe2x80x9cmountain bikesxe2x80x9d.
In general, such trailers are known and the most usual type comprises a body carried on two wheels, with the body being attached to the bicycle beneath the saddle by means of a sleeve secured to a tow bar. The trailer can thus deviate angularly to a certain extent relative to the forward direction of the bicycle. However, such a trailer is unsuitable for a cross-country bicycle since by its very nature it is required to travel over uneven ground. That is to say the trailer must have several degrees of freedom, not only relative to the forward direction of the bicycle, but also relative to the plane in which the bicycle is to be found and which may slope in various ways. Unfortunately, such a trailer is essential for those who practice off-road bicycle touring.
Proposals have already been made to provide a single-wheel trailer, with the wheel being mounted on the chassis and at the rear thereof. This makes it easier for the trailer to tilt simultaneously with the cross-country bicycle. The trailer is attached to the hub of the rear wheel, thereby enabling the center of gravity of the load to be lowered. However, overall length is increased compared with that of a bicycle fitted with a conventional trailer.
A single-wheel cross-country bicycle trailer is also known constituted by a chassis attached to the seat tube, the wheel being located at the rear end of the trailer. However, under certain conditions of difference in height, unwanted pitching is observed while cornering, particularly when the cyclist is standing on the pedals.
In both cases, a bag containing clothing and/or food is fixed on or suspended from the metal chassis.
Canadian patent CA-B-1 235 435 describes a trailer towed by a bicycle to transport objects and children simultaneously. The trailer is connected to the seat tube via a pair of hinges, one about an axis parallel to the seat tube and the other about a horizontal axis mounted in a fork that can pivot about the substantially vertical axis. However, that assembly, which is designed for transporting children, is not at all suited to a mountain bike where the tow bar of the trailer is subjected to large amounts of shear.
A first object of the invention is to mitigate the drawbacks of known devices and to enable a lightweight trailer to be made capable of being attached by means of a suitable coupling to a cross-country bicycle that travels over winding paths, and to do so without causing the bicycle to be upset.
A second object of the invention is to provide a lightweight trailer constituted essentially by a metal chassis and a shell of plastics material forming a waterproof box even though it is still necessary for objects to be stowed securely therein in order to avoid any swinging motion.
The idea on which the invention is based consists in offsetting the pivot axes of the trailer away from the seat tube.
According to the invention, a trailer for a cross-country bicycle comprising a chassis and a single wheel has a tow bar suitable for connection to the seat tube via an articulated link, and said link comprises a piece fixed to the seat tube, which piece includes a sloping portion and a portion that is substantially horizontal, a pivot axis projecting from said horizontal portion, a fork including a horizontal attachment tube of the trailer being pivotally mounted on said vertical axis, the tube of the trailer being included in a rubber sleeve integrated in the fork.
The vertical or pivot axis is preferably mounted on the bracket via a rubber ring. In this way, the trailer can move relative to the bicycle:
in azimuth, by pivoting about the vertical axis;
in elevation, by causing its tube to pivot inside the fork; and
in torsion, by elastic deformation of the sleeve and of the rubber ring, the rubber being relatively hard.
These resilient means also damp the propagation to the bicycle of any impact on the trailer, but without giving rise to oscillation.
Naturally, the terms xe2x80x9cverticalxe2x80x9d and xe2x80x9chorizontalxe2x80x9d are used to mean the positions of the various members when the bicycle and the trailer are at rest on a horizontal plane surface.
According to another characteristic of the invention, the trailer is constituted by a self-supporting tubular metal chassis covered by closed bodywork of a plastics material such as polyethylene.
The link piece between the seat tube and the tow bar is preferably molded out of a plastics material such as polyamide having hardness of 70 on the Shore scale, and constituted by two symmetrical shells assembled onto the seat tube by screws. This part of complex shape is thus made easier to manufacture.
According to yet another characteristic of the invention, the pivot axis slopes at an angle of about 5xc2x0 relative to the vertical. When the trailer is going downhill, this disposition prevents the trailer jack-knifing to left or to right of the bicycle under its own weight, thereby causing the bicycle to fall over.
Furthermore, wear rings are provided throughout the articulated coupling so they can easily be replaced, thereby giving the trailer a long lifetime.
In another embodiment, the fork is articulated on a conical pivot, at the end of a shaft secured to the fork and turning inside at least one ball bearing.